Ink composition, two-pack curing ink composition set, and recording method and recorded matter using these

ABSTRACT

The present invention provides: an ink composition which contains at least a polymerizable compound, a photopolymerization initiator and a coloring material, and is free from an aqueous solvent, wherein the polymerizable compound comprises at least a urethane oligomer; a two-pack curing ink composition set comprising an ink composition containing a coloring material and a reaction liquid containing a photopolymerization initiator and capable of forming an image with an ink composition obtained by mixing the ink composition and the reaction liquid, wherein the ink composition after mixing contains at least a polymerizable compound, a photopolymerization initiator and a coloring material, and is free from an aqueous solvent, wherein the polymerizable compound comprises a urethane oligomer.

CONTINUING APPLICATION DATA

This application is a continuation of, and claims priority under 35U.S.C. §12 to, U.S. application Ser. No. 11/998,469, filed Nov. 29,2007, the content of which is incorporated by reference herein in itsentirety.

This application also claims priority under 35 U.S.C. §119, through theabove-identified parent U.S. application, on Japanese patent applicationno. 2006-323892, filed on Nov. 30, 2006, and Japanese patent applicationno. 2007-223824, filed on Aug. 30, 2007. The content of each suchrelated application is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to an ink composition and a two-packcuring ink composition set, that cure by light such as ultraviolet rays.More particularly, it relates to an ink composition and a two-packcuring ink composition set, having excellent film strength andadditionally excellent curability. Furthermore, the present inventionrelates to a recording method and recorded matter, using the inkcomposition or the two-pack curing ink composition set.

BACKGROUND OF THE INVENTION

Ink jet recording method is a printing method which conducts printing byflying small droplets of an ink composition and attaching the same to arecording medium such as papers. This ink jet recording method has thecharacteristic that high resolution and high definition image can beprinted at high speed. In general, an ink composition used in an ink jetrecording method comprises an aqueous solvent as a main component, andfurther contains a coloring component and a wetting agent such asglycerin for the purpose of preventing clogging.

On the other hand, where printing is conducted on recording media suchas papers and clothes in which an aqueous ink composition is hard topenetrate, or materials such as metals and plastics, in which an aqueousink composition does not penetrate, such as plates or films producedfrom phenol, melamine, vinyl chloride, acryl or polycarbonate, an inkcomposition is required to contain a component that a coloring materialcan stably be fixed to a recording medium.

To such a demand, a light curing ink jet ink comprising a coloringmaterial, a light curing agent (racially polymerizable compound) and(photoradical) polymerization initiator is disclosed (for example, seePatent Document 1). It is described that this ink can prevent ink frombleeding into a recording medium, and can improve image quality.

Furthermore, to attempt improvement of film strength, chemicalresistance, dispersion stability and the like, a light curing ink jetrecording ink composition containing a coloring material, a urethaneoligomer, a monomer having trifunctional or more reactive group, and anaqueous solvent is developed (see Patent Document 2).

Moreover, for the purpose of preventing separation of a pigment as acoloring material, improving scratch resistance and printingreliability, preventing bleeding after printing and enhancing dryingproperties of an ink, an ink jet recording ink comprising two componentsof an ink composition containing a coloring material, and a reactionliquid containing a polymerization initiator, and an ink jet recordingmethod which prints on a recording medium using those two components aredisclosed (for example, see Patent Document 3).

An ink jet recording ink comprising such two components is that aphotopolymerization initiator and a light curing resin is contained ineither of the ink composition or the reaction liquid. Thus, byseparating into two components of the ink composition and the reactionliquid, dark reaction is suppressed, making it possible to store the inkcomposition and the reaction liquid over a long period of time and toobtain prints having excellent light resistance and heat resistance.

-   Patent Document 1: U.S. Pat. No. 5,623,001-   Patent Document 2: JP-A-2000-336295-   Patent Document 3: JP-A-8-218018

SUMMARY OF THE INVENTION

However, an ultraviolet curing ink composition using an aqueous solventis that the aqueous medium does not contribute to curing. As a result,water bleeds upon curing, and due to the influence, a cured product doesnot have smooth edges, lacking in sharpness.

The present invention relates to an ink composition and a two-packcuring ink composition set, which overcome the disadvantages of theprior art, have excellent film strength, chemical resistance anddispersion stability and additionally excellent curability, and can forma clear image. Furthermore, the present invention relates to a recordingmethod and recorded matter, using the ink composition and the two-packcuring ink composition set.

As a result that the present inventors have been made extensive andintensive investigations, the above objects are achieved by employingthe following constitutions, and the present invention has been made.

That is, the present invention is as follows.

(1) An ink composition which contains at least a polymerizable compound,a photopolymerization initiator and a coloring material, and is freefrom an aqueous solvent, wherein the polymerizable compound comprises atleast a urethane oligomer.

(2) The ink composition as described in (1), wherein the polymerizablecompound is a radically polymerizable compound, and thephotopolymerization initiator is a photoradical polymerizationinitiator.

(3) The ink composition as described in (1) or (2), wherein the contentof the urethane oligomer in the ink composition is from 1 to 50% byweight.

(4) The ink composition as described in (2) or (3), wherein theradically polymerizable compound comprises an allyl compound and/or anN-vinyl compound.

(5) The ink composition as described in (4), wherein the content of theallyl compound and/or N-vinyl compound is from 20 to 80% by weight.

(6) The ink composition as described in (4) or (5), wherein the allylcompound is allyl glycol.

(7) The ink composition as described in any one of (4) to (6), whereinthe N-vinyl compound is N-vinyl formamide.

(8) A two-pack curing ink composition set comprising an ink compositioncontaining a coloring material and a reaction liquid containing aphotopolymerization initiator and capable of forming an image with anink composition obtained by mixing the ink composition and the reactionliquid,

wherein the ink composition after mixing contains at least apolymerizable compound, a photopolymerization initiator and a coloringmaterial, and is free from an aqueous solvent, wherein the polymerizablecompound comprises a urethane oligomer.

(9) The two-pack curing ink composition set as described in (8), whereinthe ink composition after mixing is the ink composition as described inany one of (1) to (7).

(10) A recording method using the ink composition as described in anyone of (1) to (7), or the two-pack curing ink composition set asdescribed in any one of (8) and (9).

(11) Recorded matter obtained using the ink composition as described inany one of (1) to (7), or the two-pack curing ink composition set asdescribed in any one of (8) and (9).

The ink composition of the present invention is an ink composition whichcontains at least a polymerizable compound, a photopolymerizationinitiator and a coloring material, and is free from an aqueous solvent,wherein the polymerizable compound comprises at least a urethaneoligomer. Owing to these features, an ink composition having excellentfilm strength and additionally excellent curability and capable offorming a clear image can be provided.

Furthermore, the two-pack curing ink composition set of the presentinvention is a two-pack curing ink composition set comprising: an inkcomposition containing a coloring material; and a reaction liquidcontaining a photopolymerization initiator, and capable of forming animage with an ink composition obtained by mixing the ink composition andthe reaction liquid, wherein the ink composition after mixing containsat least a polymerizable compound, a photopolymerization initiator and acoloring material, and is free from an aqueous solvent, wherein thepolymerizable compound comprises a urethane oligomer (that is, theconstitution of the ink composition according to the present inventiondescribed above). Such a two-pack curing ink composition set makes itpossible to have excellent film strength and additionally excellentcurability and to form a clear image.

DETAILED DESCRIPTION OF THE INVENTION

The ink composition of the present invention is described in detailbelow.

The ink composition of the present invention is an ink composition whichcontains at least a polymerizable compound, a photopolymerizationinitiator and a coloring material, and does not contain an aqueoussolvent, wherein at least a urethane oligomer is contained as thepolymerizable compound.

The urethane oligomer in the present invention means a urethane oligomerhaving at least one urethane bond and radically polymerizableunsaturated double bond in the molecule. The term “oligomer” as used inthe present invention means a molecule of a medium size having astructure constituted by small number repetitions, generally from about2 to 20, of units substantially or conceptually obtained from a moleculehaving a relative molecular mass (synonymous with a molecular weight).

The urethane oligomer in the present invention has at least one acryloylgroup as a functional group, and therefore has the properties ofinducing a polymerization reaction with a monomer or the like byultraviolet irradiation or the like, thereby crosslinking andpolymerizing.

The urethane oligomer used in the present invention includes a oligomergenerated by an addition reaction of a polyol, a polyisocyanate and apolyhydroxy compound, and additionally includes a polyester typeurethane acrylate, a polyether type urethane acrylate, a polybutadienetype urethane acrylate and a polyol type urethane acrylate, depending ona molecular structure constituting a skeleton.

The urethane oligomer used in the present invention has a molecularweight in a range of from about 500 to 20,000, and preferably from about500 to 10,000.

The content of the urethane oligomer in the ink composition according tothe present invention is in a range of from about 1 to 50% by weight,and preferably from about 3 to 30% by weight.

The ink composition according to the present invention preferablycontains a photopolymerization initiator for radical polymerization orcationic polymerization as a photopolymerization initiator.

The photopolymerization initiator in the present invention is a compoundwhich induces chemical change through action of light or interactionwith electron excitation state of a sensitizing dye, thereby generatingat least one of radical, acid and base.

The photopolymerization initiator can be used by appropriately selectingfrom compounds having sensitivity to active light irradiated, such asultraviolet ray of 400 to 200 nm, far ultraviolet ray, g ray h ray, iray, KrF excimer laser light, ArF excimer light, electron beam, X ray,molecular beam or ion beam.

Specific photopolymerization initiator can use the conventionalinitiators known to one skilled in the art, and is specificallydescribed in, for example, Bruce M. Monroe et al., Chemical Revue, 93,435 (1993); P. S. Davidson, Journal of Photochemistry and Biology A:Chemistry, 73. 81 (1993); J. P. Faussier, “PhotoinitiatedPolymerization-Theory and Applications”: Rapra Review vol. 9, Report,Rapra Technology (1998); and M. Tsunooka et al., Prog. Polym. Sci., 21,1 (1996). Furthermore, many compounds used in chemical amplificationphotoresist and photocationic polymerization are described in TheJapanese Research Association of Organic Electronics Materials, ImagingOrganic Materials, pages 187-192 (1993), Bun-Shin Shuppan. Furthermore,compounds that oxidatively or reductively generate bond cleavage throughinteraction with electron excitation state of a sensitizing dye, asdescribed in, for example, F. D. Saeva, Topics in Current Chemistry,156, 59 (1990); G. G. Maslak, Topics in Current Chemistry, 168, 1(1993); H. B. Shuster et al., JACS, 112, 6329 (1990); and I. D. F. Eatonet al., JACS, 102, 3298 (1980) are known.

Preferable examples of the photopolymerization initiator include (a)aromatic ketones, (b) aromatic onium salt compounds, (c) organicperoxides, (d) hexaaryl biimidazole compounds, (e) ketoxime estercompounds, (f) borate compounds, (g) adinium compounds, (h) metallocenecompounds, (i) active ester compounds and (j) compounds havingcarbon-halogen bond.

Preferable examples of the aromatic ketones (a) include compounds havinga benzophenone skeleton or a thioxanthone skeleton, described in“RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY”, J. P. FOUASSIER,J. F. RABEK (1993), p 77 to 117.

More preferable aromatic ketones (a) include α-thiobenzophenonecompounds described in JP-B-47-6416, benzoin ether compounds describedin JP-B-47-3981, α-substituted benzoin compounds described inJP-B-47-22326, benzoin derivatives described in JP-B-47-23664,aroylphosphonic esters described in JP-A-57-30704, dialkoxybenzophenonesdescribed in JP-B-60-26483, benzoin ethers described in JP-B-60-26403and JP-A-62-81345, α-aminobenzophenones described in JP-B-1-34242, U.S.Pat. No. 4,318,791 and EP 0284561 A1, p-di(dimethylaminobenzoyl)benzenedescribed in JP-A-2-211452, thiosubstituted aromatic ketones describedin JP-A-61-194062, acylphosphine sulfides described in JP-B-2-9597,acylphosphines described in JP-B-2-9596, thioxanthones described inJP-B-63-61950 and coumalins described in JP-B-59-42864.

Examples of the aromatic onium salts (b) include elements of Groups V,VI and VII in the periodic table, specifically aromatic onium salts ofN, P, As, Sb, Bi, O, S, Se, Te and I. For example, iodonium saltsdescribed in European Patent 104143, U.S. Pat. No. 4,837,124,JP-A-2-150848 and JP-A-2-96514; sulfonium salts described in EuropeanPatents 370693, 233567, 297443, 297442, 279210 and 422570, and U.S. Pat.Nos. 3,902,144, 4,933,377, 4,760,013, 4,734,444 and 2,833,827; diazoniumsalts (such as benzene diazonium which may have a substituent);diazonium salt resins (such as formaldehyde resin ofdiazodiphenylamine); N-alkoxypyridinium salts (for example, described inU.S. Pat. No. 4,743,528, JP-A-63-138345, JP-A-63-142345, JP-A-63-142346and JP-B-46-42363, specifically 1-methoxy-4-phenylpyridiniumtetrafluoroborate and the like); and compounds described inJP-B-52-147277, 52-14278 and 52-14279 are preferably used.

The organic peroxides (c) include almost all of organic compounds havingat least one oxygen-oxygen bond in the molecule, and preferred examplesthereof include peroxide ester types such as3,3′,4,4′-tetra-(t-butylperoxycarbonyl)benzophenone,3,3′,4,4′-tetra-(t-amylperoxycarbonyl)benzophenone,3,3′,4,4′-tetra-(t-hexylperoxycarbonyl)benzophenone,3,3′,4,4′-tetra-(t-octylperoxycarbonyl)benzophenone,3,3′,4,4′-tetra-(t-cumylperoxycarbonyl)benzophenone,3,3′,4,4′-tetra-(t-isopropylcumylperoxycarbonyl)benzo-phenone, anddi-t-butylperoxyisophthalate.

Examples of the hexaaryl biimidazole include lophine dimers described inJP-B-45-37377 and JP-B-44-86516 such as2,2′-bis(o-chlorophenyl)-4,4′,5,5′-tetraphenyl biimidazole,2,2′-bis(o-bromophenyl)-4,4′,5,5′-tetraphenyl biimidazole,2,2′-bis(o,p-dichlorophenyl)-4,4′,5,5′-tetraphenyl biimidazole,2,2′-bis(o-chlorophenyl)-4,4′,5,5′-tetra(m-methoxyphenyl)biimidazole,2,2′-bis(o,o′-dichlorophenyl)-4,4′,5,5′-tetraphenyl biimidazole,2,2′-bis(o-nitrophenyl)-4,4′,5,5′-tetraphenyl biimidazole,2,2′-bis(o-methylphenyl)-4,4′,5,5′-tetraphenyl biimidazole, and2,2′-bis(o-trifluorophenyl)-4,4′,5,5′-tetraphenyl biimidazole.

Examples of the ketoxime ester include 3-benzoyloxyiminobutan-2-one,3-acetoxyiminobutan-2-one, 3-propoinyloxyiminobutan-2-one,2-acetoxyiminopentan-3-one, 2-acetoxyimino-1-phenylpropan-1-one,2-benzoyloxyimino-1-phenylpropan-1-one,3-toluenesulfonyloxyiminobutan-1-one, and2-ethoxycarbonyloxyimino-1-phenylpropan-1-one.

Examples of the borate salt (f) that is other example of thephotopolymerization initiator in the present invention include compoundsdescribed in U.S. Pat. Nos. 3,567,453 and 4,343,891, and EuropeanPatents 109,772 and 109,773. Examples of the adinium salt compound (g)that is other example of the photopolymerization initiator includecompounds having N—O bond described in JP-A-63-138345, JP-A-63-142345,JP-A-63-142346, JP-A-63-143537 and JP-B-46-42363.

Examples of the metallocene compound (h) which is other example of thephotopolymerization initiator include titanocene compounds described inJP-A-59-152396, JP-A-61-151197, JP-A-63-41484, JP-A-2-249 andJP-A-2-4705, and iron-arene complexes described in JP-A-1-304453 andJP-A-1-152109.

Specific examples of the titanocene compound includedi-cyclopentadienyl-Ti-di-chloride, di-cyclopentadienyl-Ti-bis-phenyl,di-cyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluoropheny-1-yl,di-cyclopentadienyl-Ti-bis-2,3,5,6-tetrafluoropheny-1-yl,di-cyclopentadienyl-Ti-bis-2,4,6-trifluoropheny-1-yl,di-cyclopentadienyl-Ti-2,6-difluoropheny-1-yl,di-cyclopentadienyl-Ti-bis-2,4-difluoropheny-1-yl,di-methylcyclopentadienyl-Ti-bis-2,3,4,5,6-pentafluoro-pheny-1-yl,di-methylcyclopentadienyl-Ti-bis-2,3,5,6-tetrafluoropheny-1-yl,di-methylcyclopentadienyl-Ti-bis-2,4-difluoropheny-1-yl,bis(cyclopentadienyl)-bis(2,6-difluoro-3-(pry-1-yl)phenyl)-titanium,bis(cyclopentadienyl)bis[2,6-difluoro-3-(methylsulfone-amide)phenyl]titanium,andbis(cyclopentadienyl)bis[2,6-difluoro-3-(N-butylbiaroyl-amino)phenyl]titanium.

Examples of the active ester compound (i) include nitrobenzyl estercompounds described in European Patents 0290750, 046083, 156153, 271851and 0388343, U.S. Pat. Nos. 3,901,710 and 4,181,531, JP-A-60-198538 andJP-A-53-133022; iminosulfonate compounds described in European Patents0199672, 84515, 199672, 044115 and 0101122, U.S. Pat. Nos. 4,618,564,4,371,605 and 4,431,774, JP-A-64-18143, JP-A-2-245756 and JP-A-4-365048;and compounds described in JP-B-62-6223, JP-B-63-14340 andJP-A-59-174831.

Preferable examples of the compound (j) having carbon-halogen bondinclude compounds described in Wakabayashi et al., Bull. Chem. Soc.Japan, 42, 2924 (1969), compounds described in British Patent 1,388,492,compounds described in JP-A-53-133428, and compounds described in GermanPatent 3,337,024.

Further examples include compounds described in F. C. Schaefer et al.,J. Org. Chem., 29, 1527 (1964), compounds described in JP-A-62-58241,and compounds described in JP-A-5-281728, and additionally includecompounds described in German Patent 2,641,100, compounds described inGerman Patent 3,333,450, compounds described in German Patent 3,021,590,and compounds described in German Patent 3,021,599.

Photoradical polymerization initiators commercially available in tradenames of Vicure 10 and 30 (products of Stauffer Chemical), Irgacure 127,184, 500, 651, 2959, 907, 369, 379, 754, 1700, 1800, 1850, 819, OXE01,Darocur 1173, TPO, IXT (products of Ciba Specialty Chemicals),Quantacure CTX (a product of Aceto Chemical), Kayacure DETX-S (a productof Nippon Kayaku) and ESCURE KIP150 (a product of Lamberti) can also beused.

The photopolymerization initiator is contained in the ink compositionaccording to the present invention in an amount of preferably from 1 to20% by weight, and more preferably from 3 to 15% by weight. Use of thephotopolymerization initiator in the above range exhibits the effect ofholding curability without deterioration of cured film strength.

The polymerizable compound other than the urethane oligomer used in theink composition according to the present invention is not particularlylimited and can use any compound regardless of the species of a monomer,an oligomer and a polymer so long as it is a compound which inducespolymerization reaction by giving any energy and cures. In particular,the conventional various polymerizable monomers known asphotocationically polymerizable monomers and photoradicallypolymerizable monomers, that induce polymerization reaction byinitiation species generated from a photopolymerization initiator arepreferably used.

The polymerizable compound can be used alone or a mixture of two or morethereof for the purpose of adjusting reaction rate, ink properties,cured film properties and the like. Furthermore, the polymerizablecompound may be a monofunctional compound or a multifunctional compound.

Examples of the cationically polymerizable compound used as thepolymerizable compound in the present invention include epoxy compounds,vinyl ether compounds and oxetane compounds, described in, for example,JP-A-6-9714, 2001-31892, 2001-40068, 2001-55507, 2001-310938,2001-310937 and 2001-220526.

The epoxy compound includes aromatic epoxides and alicyclic epoxides.

Examples of the monofunctional epoxy compound that can be used in thepresent invention include phenyl glycidyl ether, p-tert-butylphenylglycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, allylglycidyl ether, 1,2-butylene oxide, 1,3-bitadiene monoxide,1,2-epoxydodecane, epichlorohydrin, 1,2-epoxydecane, styrene oxide,cyclohexene oxide, 3-methacryloyloxymethylcyclohexene oxide,3-acryloyloxymethylcyclohexene oxide and 3-vinylcyclohexene oxide.

Examples of the multifunctional epoxy compound include bisphenol Adiglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidylether, brominated bisphenol A diglycidyl ether, brominated bisphenol Fdiglycidyl ether, brominated bisphenol S diglycidyl ether, epoxy novolakresin, hydrogenated bisphenol A diglycidyl ether, hydrogenated bisphenolF diglycidyl ether, hydrogenated bisphenol S diglycidyl ether,3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylate,2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane,bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate,3,4-epoxy-6-methylcyclohexyl-3′,4′-epoxy-6′-methylcyclo-hexanecarboxylate, methylenebis(3,4-epoxycyclohexane), dicyclopentadienediepoxide, ethylene glycol di(3,4-epoxycyclohexylmethyl)ether,ethylenebis(3,4-epoxycyclohexane carboxylate), dioctylepoxyhexahydrophthalate, di-2-ethylhexyl epoxyhexahydrophthalate,1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether,glycerin triglycidyl ether, trimethylolpropane triglycidyl ether,polyethylene glycol diglycidyl ether, polypropylene glycol diglycidylethers, 1,1,3-tetradecadiene dioxide, limonene dioxide,1,2,7,8-diepoxyoctane and 1,2,5,6-diepoxycyclooctane.

Of those epoxy compounds, the aromatic epoxide and alicyclic epoxide arepreferred from the standpoint of excellent curing rate, and thealicyclic epoxide is particularly preferred.

Examples of the monofunctional vinyl ether that can be used in thepresent invention include methylvinyl ether, ethylvinyl ether,propylvinyl ether, n-butylvinyl ether, t-butylvinyl ether,2-ethylhexylvinyl ether, n-nonylvinyl ether, laurylvinyl ether,cyclohexylvinyl ether, cyclohexylmethylvinyl ether,4-methylcyclohexylmethylvinyl ether, benzylvinyl ether,dicyclopentenylvinyl ether, 2-dicyclopentenoxyethylvinyl ether,methoxyethylvinyl ether, ethoxymethylvinyl ether, butoxyethylvinylether, methoxyethoxyethylvinyl ether, ethoxyethoxyethylvinyl ether,methoxypolyethylene glycol vinyl ether, tetrahydrofurfurylvinyl ether,2-hydroxyethylvinyl ether, 2-hydroxypropylvinyl ether,4-hydroxybutylvinyl ether, 4-hydroxymethylcyclohexylmethylvinyl ether,diethylene glycol monovinyl ether, polyethylene glycol vinyl ether,chloroethylvinyl ether, chlorobutylvinyl ether, chloroethoxyethylvinylether, phenylethylvinyl ether and phenoxypolyethylene glycol vinylether.

Examples of the multifunctional vinyl ether include divinyl ethers suchas ethylene glycol divinyl ether, diethylene glycol divinyl ether,polyethylene glycol divinyl ether, propylene glycol divinyl ether,butylene glycol divinyl ether, hexanediol divinyl ether, bisphenol Aalkylene oxide divinyl ether and bisphenol F alkylene oxide divinylether; and multifunctional vinyl ethers such as trimethylolethanetrivinyl ether, trimethylolpropane trivinyl ether, ditrimethylolpropanetetravinyl ether, glycerin trivinyl ether, pentaerythritol hexavinylether, dipentaerythritol pentavinyl ether, dipentaerythritol hexavinylether, ethylene oxide-added trimethylolpropane trivinyl ether, propyleneoxide-added trimethylolpropane trivinyl ether, ethylene oxide-addedditrimethylolpropane tetravinyl ether, propylene oxide-addedditrimethylolpropane tetravinyl ether, ethylene oxide-addedpentaerythritol tetravinyl ether, propylene oxide-added pentaerythritoltetravinyl ether, ethylene oxide-added dipentaerythritol hexavinylether, and propylene oxide-added dipentaerythritol hexavinyl ether.

The vinyl ether compound is preferably a di- or trivinyl ether compoundfrom the standpoints of curability, adhesion to a medium to be recorded,surface hardness of image formed, and the like, and a divinyl ethercompound is particularly preferred.

The oxetane compound in the present invention means a compound having anoxetane ring, and the conventional oxetane compounds as described inJP-A-2001-220526, 2001-310937 and 2003-341217 can optionally be selectedand used.

The compound having an oxetane ring that can be used in the presentinvention is preferably a compound having from 1 to 4 oxetane rings inits structure. Use of such a compound makes it easy to maintain aviscosity of an ink composition in a range of good handling properties,and can obtain high adhesion of ink after curing to a medium to berecorded.

Examples of the monofunctional oxetane used in the present inventioninclude 3-ethyl-3-hydroxymethyloxetane,3-(meth)allyloxymethyl-3-ethyloxetane,(3-ethyl-3-oxetanylmethoxy)methylbenzene,4-fluoro-[1-(3-ethyl-3-oxetanylmethoxy)methyl]benzene,4-methoxy-[1-(3-ethyl-3-oxetanylmethoxy)methyl]benzene,[1-(3-ethyl-3-oxetanylmethoxy)ethyl]phenyl ether,isobutoxymethyl(3-ethyl-3-oxetanylmethyl)ether,isobornyloxyethyl(3-ethyl-3-oxetanylmethyl)ether,isobornyl(3-ethyl-3-oxetanylmethyl)ether,2-ethylhexyl(3-ethyl-3-oxetanylmethyl)ether, ethyl diethyleneglycol(3-ethyl-3-oxetanylmethyl)ether,dicyclopentadiene(3-ethyl-3-oxetanylmethyl)ether,dicyclopentenyloxyethyl(3-ethyl-3-oxetanylmethyl)ether,dicyclopentenyl(3-ethyl-3-oxetanylmethyl)ether,tetrahydrofurfuryl(3-ethyl-3-oxetanylmethyl)ether,tetrabromophenyl(3-ethyl-3-oxetanylmethyl)ether,2-tetrabromophenoxyethyl(3-ethyl-3-oxetanylmethyl)ether,tribromophenyl(3-ethyl-3-oxetanylmethyl)ether,2-tribromophenoxyethyl(3-ethyl-3-oxetanylmethyl)ether,2-hydroxyethyl(3-ethyl-3-oxetanylmethyl)ether,2-hydroxypropyl(3-ethyl-3-oxetanylmethyl)ether,butoxyethyl(3-ethyl-3-oxetanylmethyl)ether,pentachlorophenyl(3-ethyl-3-oxetanylmethyl)ether,pentabromo(3-ethyl-3-oxetanylmethyl)ether, andbornyl(3-ethyl-3-oxetanylmethyl)ether.

Examples of the multifunctional oxetane include3,7-bis(3-oxetanyl)-5-oxa-nonane,3,3′-(1,3-(2-methylenyl)propanediylbis(oxymethylene)bis-(3-ethyloxetane),1,4-bis[(3-ethyl-3-oxetanylmethoxy)methyl]benzene,1,2-bis[(3-ethyl-3-oxetanylmethoxy)methyl]ethane,1,3-bis[(3-ethyl-3-oxetanylmethoxy)methyl]propane, ethylene glycolbis(3-ethyl-3-oxetanylmethyl)ether, dicyclopentenylbis(3-ethyl-3-oxetanylmethyl)ether, triethylene glycolbis(3-ethyl-3-oxetanylmethyl)ether, tetraethylene glycolbis(3-ethyl-3-oxetanylmethyl)ether,tricyclodecanediyldimethylene(3-ethyl-3-oxetanylmethyl)-ether,trimethylolpropane tris(3-ethyl-3-oxetanylmethyl)ether,1,4-bis(3-ethyl-3-oxetanylmethoxy)butane,1,6-bis(3-ethyl-3-oxetanylmethoxy)hexane, pentaerythritoltris(3-ethyl-3-oxetanylmethyl)ether, pentaerythritoltetrakis(3-ethyl-3-oxetanylmethyl)ether, polyethylene glycolbis(3-ethyl-3-oxetanylmethyl)ether, dipentaerythritolhexakis(3-ethyl-3-oxetanylmethyl)ether, dipentaerythritolpentakis(3-ethyl-3-oxetanylmethyl)ether, dipentaerythritoltetrakis(3-ethyl-3-oxetanylmethyl)ether, caprolactone-modifieddipentaerythritol hexakis(3-ethyl-3-oxetanylmethyl)ether,caprolactone-modified dipentaerythritolpentakis(3-ethyl-3-oxetanylmethyl)ether, ditrimethylolpropanetetrakis(3-ethyl-3-oxetanylmethyl)-ether, EO-modified bisphenol Abis(3-ethyl-3-oxetanylmethyl)ether, PO-modified bisphenol Abis(3-ethyl-3-oxetanylmethyl)ether, EO-modified hydrogenated bisphenol Abis(3-ethyl-3-oxetanylmethyl)ether, PO-modified hydrogenated bisphenol Abis(3-ethyl-3-oxetanylmethyl)ether, and EO-modified bisphenol F(3-ethyl-3-oxetanylmethyl)ether.

Such compounds having an oxetane ring are described in detail inJP-A-2003-341217, paragraphs 0021 to 0048, and the compounds describedtherein can suitably be used in the present invention.

Of the oxetane compounds used in the present invention, a compoundhaving 1 to 2 oxetane rings is preferably used from the standpoints ofviscosity and adhesion of an ink composition.

In the ink composition of the present invention, those polymerizablecompounds may be used alone or as mixtures of two or more thereof, otherthan the urethane oligomer. From the standpoint of effectivelysuppressing shrinkage at the time of ink curing, at least one oxetanecompound and at least one selected from an epoxy compound and a vinylether compound are preferably used together.

It is preferred in the present invention to use conventional variousradically polymerizable compounds that induce polymerization reaction byinitiation species generated from a photoradical initiator, as thepolymerizable compound.

Examples of the radically polymerizable monomer include (meth)acrylates,(meth)acryl amides and aromatic vinyls. In the description, when both orany one of “acrylate” and “methacrylate” are intended, it is described“(meth)acrylate”, and when both or any one of “acryl” and “methacryl”are intended, it is described “(meth)acryl”.

The (meth)acrylate used in the present invention includes the followingcompounds.

Examples of the monofunctional (meth)acrylate include hexyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, tert-octyl (meth)acrylate,isoamyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate,stearyl (meth)acrylate, isostearyl (meth)acrylate, cyclohexyl(meth)acrylate, 4-n-butylcyclohexyl (meth)acrylate, bornyl(meth)acrylate, isobornyl (meth)acrylate, benzyl (meth)acrylate,2-ethylhexyl diglycol (meth)acrylate, butoxyethyl (meth)acrylate,2-chloroethyl (meth)acrylate, 4-bromobutyl (meth)acrylate, cyanoethyl(meth)acrylate, benzyl (meth)acrylate, butoxymethyl (meth)acrylate,3-methoxybutyl (meth)acrylate, alkoxymethyl (meth)acrylate, alkoxyethyl(meth)acrylate, 2-(2-methoxyethoxy)ethyl (meth)acrylate,2-(2-butoxyethoxy)ethyl (meth)acrylate, 2,2,2-tetrafluoroethyl(meth)acrylate, 1H, 1H, 2H, 2H-perfluorodecyl (meth)acrylate,4-butylphenyl (meth)acrylate, phenyl (meth)acrylate,2,4,5-tetramethylphenyl (meth)acrylate, 4-chlorophenyl (meth)acrylate,phenoxymethyl (meth)acrylate, phenoxyethyl (meth)acrylate, glycidyl(meth)acrylate, glycidyloxybutyl (meth)acrylate, glycidyloxyethyl(meth)acrylate, glycidyloxypropyl (meth)acrylate, tetrahydrofurfuryl(meth)acrylate, hydroxyalkyl (meth)acrylate, 2-hydroxyethyl(meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl(meth)acrylate, 3-hydroxypropyl (meth)acrylate, dimethylaminoethyl(meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl(meth)acrylate, diethylaminopropyl (meth)acrylate, trimethoxysilylpropyl(meth)acrylate, trimethylsilylpropyl (meth)acrylate, polyethylene oxidemonomethyl ether (meth)acrylate, oligoethylene oxide monomethyl ether(meth)acrylate, polyethylene oxide (meth)acrylate, oligoethylene oxide(meth)acrylate, oligoethylene oxide monoalkyl ether (meth)acrylate,polyethylene oxide monoalkyl ether (meth)acrylate, dipropylene glycol(meth)acrylate, polypropylene oxide monoalkyl ether (meth)acrylate,oligopropylene oxide monoalkyl ether (meth)acrylate,2-methacryloyloxythyl succinic acid, 2-methacryloyloxyhexahydrophthalicacid, 2-methacryloyloxyethyl-2-hydroxypropyl phthalate, butoxydiethyleneglycol (meth)acrylate, trifluoroethyl (meth)acrylate,perfluorooctylethyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl(meth)acrylate, EO-modified phenol (meth)acrylate, EO-modified cresol(meth)acrylate, EO-modified nonylphenol (meth)acrylate, PO-modifiednonylphenol (meth)acrylate, and EO-modified-2-ethylhexyl (meth)acrylate.

Examples of the bifunctional (meth)acrylate include 1,6-hexanedioldi(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycoldi(meth)acrylate, 2,4-dimethyl-1,5-pentanediol di(meth)acrylate, butylethyl propane di(meth)acrylate, ethoxylated cyclohexane methanoldi(meth)acrylate, polyethylene glycol di(meth)acrylate, oligoethyleneglycol di(meth)acrylate, ethylene glycol di(meth)acrylate,2-ethyl-2-butyl-butanediol di(meth)acrylate, hydroxypivalic acidneopentyl glycol di(meth)acrylate, EO-modified bisphenol Adi(meth)acrylate, bisphenol F polyethoxy di(meth)acrylate, polypropyleneglycol di(meth)acrylate, oligopropylene glycol di(meth)acrylate,1,4-butanediol di(meth)acrylate, 2-ethyl-2-butylpropanedioldi(meth)acrylate, 1,9-nonane di(meth)acrylate, propoxylated ethoxylatedbisphenol A di(meth)acrylate, and tricyclodecane di(meth)acrylate.

Examples of the trifunctional (meth)acrylate include trimethylolpropane(meth)acrylate, trimethylolethane (meth)acrylate, alkyleneoxide-modified tri(meth)acrylate of trimethylolpropane, pentaerythritoltri(meth)acrylate, dipentaerythritol tri(meth)acrylate,trimethylolpropane tri((meth)acryloyloxypropane)ether, isocyanuric acidalkylene oxide-modified tri(meth)acrylate, propionic aciddipentaerythritol tri(meth)acrylate,tri((meth)acryloyloxyethyl)isocyanurate, hydroxypivalaldehyde-modifieddimethylolpropane tri(meth)acrylate, sorbitol tri(meth)acrylate,propoxylated trimethylolpropane tri(meth)acrylate, and ethoxylatedglycerin triacrylate.

Examples of the tetrafunctional (meth)acrylate include pentaerythritoltetra(meth)acrylate, sorbitol tetra(meth)acrylate, ditrimethylolpropanetetra(meth)acrylate, propionic acid dipentaerythritoltetra(meth)acrylate, and ethoxylated pentaerythritoltetra(meth)acrylate.

Examples of the pentafunctional (meth)acrylate include sorbitolpenta(meth)acrylate, and dipentaerythritol penta(meth)acrylate.

Examples of the hexa(meth)acrylate include dipentaerythritolhexa(methacrylate), sorbitol hexa(methacrylate), alkylene oxide-modifiedhexa(methacrylate) of phosphazene, and caprolacton-modifieddipentaerythritol hexa(meth)acrylate.

Examples of the (meth)acrylamides used in the present invention include(meth)acrylamide, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide,N-propyl (meth)acrylamide, N-n-butyl (meth)acrylamide, N-t-butyl(meth)acrylamide, N-butoxymethyl (meth)acrylamide, N-isopropyl(meth)acrylamide, N-methylol (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl (meth)acrylamide, and (meth)acryloylmorpholine.

Examples of the aromatic vinyls used in the present invention includestyrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene,isopropylstyrene, chloromethylstyrene, methoxystyrene, acetoxystyrene,chlorostyrene, dichlorostyrene, bromostyrene, vinylbenzoic acid methylester, 3-methylstyrene, 4-methylstyrene, 3-ethylstyrene, 4-ethylstyrene,3-propylstyrene, 4-propylstyrene, 3-butylstyrene, 4-butylstyrene,3-hexylstyrene, 4-hexylstyrene, 3-octylstyrene, 4-octylstyrene,3-(2-ethylhexyl)styrene, 4-(2-ethylhexyl)styrene, allylstyrene,isopropenylstyrene, butenylstyrene, octenylstyrene,4-t-butoxycarbonylstyrene, 4-methoxystyrene and 4-t-butoxystyrene.

Examples of the radically polymerizable monomer in the present inventioninclude vinyl esters (vinyl acetate, vinyl propionate, vinyl versatateand the like), allyl esters (allyl acetate and the like),halogen-containing monomers (vinylidene chloride, vinyl chloride and thelike), vinyl ethers (methyl vinyl ether, butyl vinyl ether, hexyl vinylether, methoxyvinyl ether, 2-ethylhexylvinyl ether, methoxyethylvinylether, cyclohexylvinyl ether, chloroethylvinyl ether and the like),vinyl cyanate ((meth)acrylonitrile and the like), and olefins (ethylene,propylene and the like).

Of those, as the radically polymerizable monomers in the presentinvention, (meth)acrylates and (meth)acrylamides are preferred from thepoint of curing rate, and tetrafunctional or more (meth)acrylates areparticularly preferred from the point of curing rate. Furthermore, it ispreferred to use the multifunctional (meth)acrylates in combination withmonofunctional or bifunctional (meth)acrylates, and (meth)acrylamidefrom the standpoint of viscosity of an ink composition.

It is suitable that the content of the polymerizable compound in an inkcomposition is from 50 to 95% by mass based on the total solid contentof the composition. The content is in a range of preferably from 60 to92% by weight, and more preferably from 70 to 90% by weight.

It is preferred that the monomer used in the present invention has PIIvalue (Primary Irritation Index) of 2 or less.

Monofunctional monomers, bifunctional monomers and multifunctionalmonomers, having PII value of 2 or less used in the present inventionare shown in Table 1 below.

TABLE 1 Viscosity Material name (mPa · s) P.I.I Monofunctional monomer(2-Methyl-2-ethyl-1,3-dioxolan-4-yl)methyl 5.1 1.3 acrylate (MEDOL-10,Osaka Organic Chemical) (2-Ethyl-2-isobutyl-1,3-dioxolan-4-yl)methyl 5.31.0 acrylate (MIBDOL-10, Osaka Organic Chemical) Phenoxyethyl acrylate3.3 1.7 (VISCOAT #192, Osaka Organic Chemical) Isobornyl acrylate 2.60.6 (IBXA, Osaka Organic Chemical) Methoxydiethylene glycol monoacrylate2 0.7 (BLEMMER PME-100, NOF Corporation) Acryloyl morpholine (ACMO,Kohjin Co.) 12 0.5 Bifunctional monomer Ethylene glycol dimethacrylate 30.6 (LIGHT-ESTER EG, Kyoeisha Chemical Co.) Diethylene glycoldimethacrylate 5 0.5 (LIGHT-ESTER 2EG, Kyoeisha Chemical Co.)Tripropylene glycol diacrylate 12 1.6 (ARONIX M-220, Toagosei Co.)1,9-Nonanediol diacrylate 21 2.0 (VISCOAT #260, Osaka Organic Chemical)Polyethylene glycol #400 diacrylate 58 0.4 (NK ESTER A400, Shin-NakamuraChemical) Tetraethylene glycol dimethacrylate 14 0.5 (NK ESTER 4G,Shin-Nakamura Chemical) 1,6-Hexanediol dimethacrylate 6 0.5 (NK ESTERHD-N, Shin-Nakamura Chemical) Neopentyl glycol dimethacrylate 7 0.0 ((NKESTER NPG, Shin-Nakamura Chemical) 2-Hydroxy-1,3-dimethacryloxypropane37 0.6 (NK ESTER 701, Shin-Nakamura Chemical) 1,4-Butanedioldimethacrylate 7 2.0 ((BD, Shin-Nakamura Chemical) Multifunctionalmonomer Trimethylolpropane trimethacrylate 42 0.8 (NK ESTER TMPT,Shin-Nakamura Chemical) Trimethylolpropane-modified triacrylate 55 1.5(VISCOAT #360, Osaka Organic Chemical) Trimethylolpropane PO-modifiedtriacrylate 60 0.1 (NEW FRONTIER TMP-3P, Dai-Ichi Kogyo Seiyaku)Glycerin PO-modified triacrylate 75 0.8 (VISCOAT #GPT, Osaka OrganicChemical)

Viscosity in the above Table is the measurement value at 25° C.

In the present invention, compounds having an allyl group and compoundshaving an N-vinyl group are preferably used as the polymerizablecompound.

The compound having an allyl group as the polymerizable compound in thepresent invention is the generic name of compounds having a 2-propenylstructure (—CH₂CH═CH₂). The 2-propenyl group is called an allyl group,and is a common expression in IUPAC nomenclature system.

Examples of the compound having an allyl group include allyl glycol (aproduct of Nippon Nyukazai Co.); trimethylolpropane diallyl ether,pentaerythritol triallyl ether and glycerin monoallyl ether (products ofDaiso Co.); and polyoxyalkylene compounds having an allyl group as tradenames of UNIOX, UNIROOVE, POLYCERIN and UNISAFE (products of NOFCorporation).

In the present invention, examples of the compound having an N-vinylgroup include N-vinyl formamide, N-vinyl carbazole, N-vinyl acetamide,N-vinyl pyrrolidone, N-vinyl caprolactam and their derivatives. N-vinylformamide is particularly preferred.

Where the addition amount of the allyl group-containing compound and/orN-vinyl formamide is less than 20% by weight, there are problems onviscosity, dispersion stability, storage stability and the like of anink composition. Where the addition amount exceeds 80% by weight,curability and film strength as an ink composition may be insufficient.Therefore, the addition amount is preferably from 20 to 80% by weight,and more preferably from 20 to 70% by weight.

The ink composition of the present invention may contain apolymerization accelerator.

The polymerization accelerator is not particularly limited, and examplesthereof include Darocur EHA and EDB (products of Ciba SpecialtyChemicals).

When the polymerizable compound is a radically polymerizable compound,the ink composition of the present invention preferably contains a heatradical polymerization inhibitor. Use of the inhibitor improves storagestability of the ink composition. The heat radical polymerizationinhibitor includes Irgastab UV-10 (a product of Ciba SpecialtyChemicals).

The ink composition of the present invention can use a surfactant. Forexample, as a silicone surfactant, it is preferred to use apolyester-modified silicone and a polyether-modified silicone, and it isparticularly preferred to use a polyether-modified polydimethylsiloxaneor a polyester-modified polydimethylsiloxane. Specific examples thereofinclude BYK-347, BYK-348, and BYK-UV3500, 3510, 3530 and 3570 (productsof BYK-Chemie Japan)

The ink composition of the present invention contains a coloringmaterial.

The coloring material used may be either of dyes and pigments, but useof pigments is advantageous from the point of durability of printedmatters.

The dyes used in the present invention can use various dyes generallyused in ink jet recording, such as direct dyes, acid dyes, edible dyes,basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes andreaction disperse dyes.

The pigments used in the present invention can use inorganic pigmentsand organic pigments without particular limitation.

The inorganic pigment can use titanium oxide and iron oxide, andadditionally can use carbon black produced by the conventional methodssuch as contact method, furnace method and thermal method. The organicpigment that can be used includes azo pigments (including azo lake,insoluble azo pigment, condensed azo pigment, chelate azo pigment andthe like), polycyclic pigments (for example, phthalocyanine pigment,perylene pigment, perylone pigment, anthraquinone pigment, quinacridonepigment, dioxazine pigment, thioindigo pigment, isoindolinone pigmentand quinofuralone pigment), dye chelates (for example, basic dye chelateand acidic dye chelate), nitro pigments, nitroso pigments and anilineblack.

As the specific examples of the pigments, examples of carbon blackinclude C. I. pigment black 7; No. 2300, No. 900, MCF88, No. 33, No. 40,No. 45, No. 52, MA7, MA8, MA100 and No. 2200, products of MitsubishiChemical Corporation; Raven 5750, 5250, 5000, 3500, 1255 and 700,products of Colombian Chemicals; Regal 400R, 330R and 660R, Mogul L and700, and Monarch 800, 880, 900, 1000, 1100, 1300 and 1400, products ofCabot Corporation; and Color Black FW1, FW2, FW2V, FW18 and FW200, ColorBlack 5150, S160 and 5170, Printex 35, U, V and 140U, and Special Black6, 5, 4A and 4, products of Tegussa Co.

Examples of the pigment used in a yellow ink include C. I. PigmentYellow 1, 2, 3, 12, 13, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109,110, 114, 120, 128, 129, 138, 150, 151, 154, 155, 180, 185 and 213.

Examples of the pigment used in a magenta ink include C. I. Pigment Red5, 7, 12, 48(Ca), 48(Mn), 57(Ca), 57:1, 112, 122, 123, 168, 184, 202 and209, and Pigment Violet 19.

Examples of the pigment used in a cyan ink include C. I. Pigment Blue 1,2, 3, 15:3, 15:4, 60, 16 and 22.

According to the preferred embodiment of the present invention, thepigment has an average particle diameter in a range of preferably from10 to 200 nm, and more preferably from about 50 to 150 nm. The additionamount of the coloring material in the ink composition is in a range ofpreferably from 0.1 to 25% by mass, and more preferably from about 0.5to 15% by mass.

According to the preferred embodiment of the present invention, thosepigments are dispersed in a monomer medium with a dispersing agent or asurfactant to obtain a pigment dispersion, which may be used as an inkcomposition. Dispersing agents commonly used to prepare a pigmentdispersion, for example, a polymer dispersing agent, can be used as thepreferred dispersing agent.

Where the ink composition contains a coloring material, the inkcomposition containing the coloring material may comprise plural inkcompositions of respective colors. For example, where in addition tofour fundamental colors of yellow, magenta, cyan and black, dark colorand/or light color of the same color series are to be added for therespective color, examples thereof include light magenta (light color)and red (dark color) for magenta, light cyan (light color) and blue(dark color) for cyan, and gray and light black (light colors) and matblack (dark color) for black.

Wetting agents, penetrating agents, pH regulators, preservatives,mildewcides and the like may be added to the ink composition of thepresent invention as conventional other components that can be used inan ink.

Besides, leveling additives, matte agents, and polyester resins,polyurethane resins, vinyl resins, acrylic resins, rubber resins andwaxes for adjusting film properties can be added according to need.

When the ink composition of the present invention is used in an ink jetrecording method, it is preferred in use that the ink composition hasviscosity of 10 mPa·s or less at 25° C.

When the ink composition of the present invention is a light curing inkcomposition, curing reaction is conducted by light irradiation. When theink composition of the present invention is an ultraviolet curing inkcomposition, the ink composition is discharged on a recording medium,and is then irradiated with ultraviolet rays.

When the two-pack curing ink composition set of the present invention isa light curing ink composition set, curing reaction is conducted bymixing an ink composition containing a coloring material and a reactionliquid containing a photopolymerization initiator, and then irradiatingwith light (preferably ultraviolet rays). Mixing may be conducted beforeor after printing so long as it is before curing reaction. Specifically,the mixing and printing may have the embodiment that the ink compositioncontaining a coloring material and the reaction liquid containing aphotopolymerization initiator are deposited on a recording medium at thesame position, or may have the embodiment that the ink compositioncontaining a coloring material and the reaction liquid containing aphotopolymerization initiator are mixed, and then deposited on arecording medium.

The two-pack curing ink composition set of the present invention doesnot have any particular limitation on the formation of the inkcomposition containing a coloring material and the reaction liquidcontaining a photopolymerization initiator so long as, in the state ofmixing the ink composition containing a coloring material and thereaction liquid containing a photopolymerization initiator, such amixture is the ink composition according to the present invention asdescribed above (that is, an ink composition that contains at least apolymerizable compound, a photopolymerization initiator and a coloringmaterial, and that does not contain an aqueous solvent, wherein at leasta urethane oligomer is contained as the polymerizable compound).

Irradiation light source is not particularly limited, but theirradiation light source is preferably light having a wavelength of from350 to 450 nm.

Irradiation amount of ultraviolet rays is in a range of from 10 to20,000 mJ/cm², and preferably from 50 to 15,000 mJ/cm². Ultravioletirradiation amount in a range of such a degree enables curing reactionto sufficiently conduct.

Ultraviolet irradiation is conducted with lamps, and examples of thelamp include metal halide lamp, xenon lamp, carbon arc lamp, chemicallamp, low pressure mercury lamp and high pressure mercury lamp. Forexample, commercially available lamps such as H lamp, D lamp and V lamp,products of Fusion System, can be used.

Furthermore, ultraviolet irradiation can be conducted with ultravioletlight-emitting semiconductor elements such as ultraviolet light-emittingdiode (ultraviolet LED) and ultraviolet light-emitting semiconductorlaser.

The recording method of the ink composition and two-pack curingcomposition set according to the present invention are suitably used inink jet, UV flexo printing, UV gravure printing and the like, and canform a clear image having excellent film strength and additionallyexcellent curability.

EXAMPLES

The present invention will be illustrated in greater detail by referenceto the following Examples, but the invention should not be construed asbeing limited thereto.

Examples 1 to 12 and Comparative Examples 1 to 8

(Preparation of Pigment Dispersion)

In the Examples and Comparative Examples, the pigment dispersion wasprepared by the following method.

Allyl glycol (a product of Nippon Nyukazai Co.) as a monomer was addedto 15% by weight of C. I. Pigment Black 7 (carbon black) as a coloringmaterial and 3.5% by weight of DISCOL N-509 (a product of DainichiseikaColor & Chemicals Mfg. Co.) to make the whole 100% by weight, followedby mixing and stirring to obtain a mixture. This mixture was subjectedto dispersion treatment together with zirconia beads (diameter 1.5 mm)for 6 hours using a sand mill (a product of Yasukawa Seisakusho).

Thereafter, zirconia beads were separated with a separator to obtain ablack pigment dispersion.

Pigment dispersions corresponding to the respective colors, specificallycyan pigment dispersion 4 (C. I. Pigment Blue 15:3), magenta pigmentdispersion (C. I. Pigment Violet 19) and yellow pigment dispersion (C.I. Pigment Yellow 155), were prepared in the same manner as above.

(Preparation of Ink Composition)

In the Examples and the Comparative Examples, a polymerizable compound,a photoradical polymerization initiator and a dispersing agent weremixed and completely dissolved to prepare an ink composition. Theabove-described pigment dispersion was gradually added dropwise to anink solvent of the ink composition while stirring the pigmentdispersion. After completion of the dropwise addition, the resultingmixture was mixed and stirred at ordinary temperature for 1 hour toobtain an ink composition. The respective ink composition was filteredwith a membrane filter of 5 μm to obtain the desired ink composition.Ink compositions of the Examples (Examples 1 to 12) and the ComparativeExamples (Comparative Examples 1 to 8) are shown in Tables 2 to 6 (thenumerical values in the Tables are “% by weight”).

TABLE 2 Example 1 Example 2 Example 3 Example 4 Allyl glycol 74.3 74.374.1 74.1 N-vinylformamide Urethane oligomer 17 17 17 17 (U-15HA, aproduct of Shin-Nakamura Chemical) Irgacure 819 4 4 4 4 Irgacure 127 1 11 1 Pigment Black 7 3 Pigment Blue 15:3 3 Pigment Violet 19 3 PigmentYellow 155 3 Dispersing agent 0.7 0.7 0.9 0.6

TABLE 3 Example 5 Example 6 Example 7 Example 8 Allyl glycol 49.3 49.349.1 49.4 N-vinylformamide 25 25 25 25 Urethane oligomer 17 17 17 17(U-15HA, a product of Shin-Nakamura Chemical) Irgacure 819 4 4 4 4Irgacure 127 1 1 1 1 Pigment Black 7 3 Pigment Blue 15:3 3 PigmentViolet 19 3 Pigment Yellow 155 3 Dispersing agent 0.7 0.7 0.9 0.6

TABLE 4 Com- Com- Comparative Comparative parative parative Example 1Example 2 Example 3 Example 4 Allyl glycol 66.3 66.3 66.1 66.4N-vinylformamide 25 25 25 25 Irgacure 819 4 4 4 4 Irgacure 127 1 1 1 1Pigment Black 7 3 Pigment Blue 15:3 3 Pigment Violet 19 3 Pigment Yellow155 3 Dispersing agent 0.7 0.7 0.9 0.6

TABLE 5 Com- Com- Comparative Comparative parative parative Example 5Example 6 Example 7 Example 8 Allyl glycol 64.3 64.3 64.1 64.4 Urethaneoligomer 17 17 17 17 (U-15HA, a product of Shin-Nakamura Chemical)Irgacure 819 4 4 4 4 Irgacure 127 1 1 1 1 Pigment Black 7 3 Pigment Blue15:3 3 Pigment Violet 19 3 Pigment Yellow 155 3 Dispersing agent 0.7 0.70.9 0.6 Water 10 10 10 10

TABLE 6 Exam- ple 9 Example 10 Example 11 Example 12 Trimethylolpropane76.3 76.3 76.1 76.4 diallyl ether Urethane oligomer 15 15 15 15 (U-15HA,a product of Shin-Nakamura Chemical) Irgacure 819 4 4 4 4 Irgacure 127 11 1 1 Pigment Black 7 3 Pigment Blue 15:3 3 Pigment Violet 19 3 PigmentYellow 155 3 Dispersing agent 0.7 0.7 0.9 0.6(Film Characteristic Test)

The above ink composition was put in drops on a glass substrate, andirradiated with ultraviolet rays having a wavelength of 365 nm under theconditions such that irradiation intensity is 17 mW/cm², irradiationtime is 6 seconds and cumulative light amount is 102 mJ/cm² to cure theink composition. The ink composition of the Comparative Examples was putin drops as it is on a glass substrate, and subjected to the ultravioletirradiation and curing treatment.

Visual evaluation of surface state and the like was conducted by thefollowing indexes.

A: Scratches are not formed with nail scrubbing.

B: Curing is not sufficient, and film is peeled with nail scrubbing.

(Bleeding Characteristic Evaluation)

In the above visual evaluation, bleeding characteristic evaluation wasconducted on the ink compositions of the Examples and the ComparativeExamples by the following indexes.

A: Edge portion is sharply cured.

B: Bleeding out is generated, and edge portion is jagged.

TABLE 7 Example 1 Example 2 Example 3 Example 4 Film A A A Acharacteristic evaluation Bleeding A A A A characteristic evaluation

TABLE 8 Example 5 Example 6 Example 7 Example 8 Film A A A Acharacteristic evaluation Bleeding A A A A characteristic evaluation

TABLE 9 Comparative Comparative Comparative Comparative Example 1Example 2 Example 3 Example 4 Film B B B B characteristic evaluationBleeding A A A A characteristic evaluation

TABLE 10 Comparative Comparative Comparative Comparative Example 5Example 6 Example 7 Example 8 Film B B B B characteristic evaluationBleeding B B B B characteristic evaluation

TABLE 11 Example 9 Example 10 Example 11 Example 12 Film A A A Acharacteristic evaluation Bleeding A A A A characteristic evaluation

As is apparent from Tables 7 to 11, each ink composition of each Exampleaccording to the present invention obtains the satisfactory results inthe film characteristic evaluation and the bleeding characteristicevaluation, and can sufficiently be used as an ink composition havingexcellent film strength and additionally excellent curability.

Examples 13 to 16

(Preparation of Pigment Dispersion)

In the Examples and the Comparative Examples, the pigment dispersion wasprepared by the following method.

Allyl glycol (a product of Nippon Nyukazai Co.) as a monomer was addedto 15% by weight of C. I. Pigment Black 7 (carbon black) as a coloringmaterial and 3.5% by weight of Discol N-509 (a product of DainichiseikaColor & Chemicals Mfg. Co.) to make the whole 100% by weight, followedby mixing and stirring to obtain a mixture. This mixture was subjectedto dispersion treatment together with zirconia beads (diameter 1.5 mm)for 6 hours using a sand mill (a product of Yasukawa Seisakusho).

Thereafter, zirconia beads were separated with a separator to obtain ablack pigment dispersion.

Pigment dispersions corresponding to the respective colors, specificallycyan pigment dispersion 4 (C. I. Pigment Blue 15:3), magenta pigmentdispersion (C. I. Pigment Violet 19) and yellow pigment dispersion (C.I. Pigment Yellow 155), were prepared in the same manner as above.

(Preparation of Two-Pack Light Curing Ink Composition Set)

[Preparation of Reaction Liquid A1-4]

Allyl glycol, tripropylene glycol diacrylate and a photoradicalpolymerization initiator (Irgacure 819 and 127) were mixed in theformulation (wt %) shown in Table 12 below to completely dissolvingthose. The resulting mixture was filtered with a membrane filter of 5 μmto obtain reaction liquid A1-4.

[Preparation of Ink Composition B1-4]

Allyl glycol, a urethane oligomer and a dispersing agent were mixed inthe formulation (wt %) shown in Table 12 below to completely dissolvingthose. The above-prepared pigment dispersion (Pigment Black 7, PigmentBlue 15:3, Pigment Violet 19 and Pigment Yellow 155) was added dropwiseto the mixture obtained above while stirring (the addition amounts areshown in Table 12 below). After completion of the dropwise addition, theresulting mixture was mixed and stirred at ordinary temperature for 1hour. The mixture was then filtered with a membrane filter of 5 μm toobtain ink composition B1-4.

Two-pack light curing ink composition sets of Examples 13 to 16 areshown in Table 12.

(Film Characteristic Test)

The reaction liquid (kind A) and the ink composition (kind B) as thetwo-pack curing ink composition set prepared above were put in drops ona glass substrate and then mixed, and the resulting mixture wasirradiated with ultraviolet rays having a wavelength of 365 nm under theconditions such that irradiation intensity is 17 mW/cm², irradiationtime is 6 seconds and cumulative light amount is 102 mJ/cm² to cure themixed ink composition. Visual evaluation of surface state and the likewas conducted in the same manner as in Example 1. The results are shownin Table 13.

TABLE 12 Example Example Example Example 13 14 15 16 A1 B1 A2 B2 A3 B3A4 B4 Allyl glycol 70 79.3 70 79.3 70 79.1 70 79.4 N-vinylformamide 2525 25 25 Urethane oligomer 17 17 17 17 (U-15HA, a product ofShin-Nakamura Chemical) Irgacure 819 4 4 4 4 Irgacure 127 1 1 1 1Pigment Black 7 3 Pigment Blue 15:3 3 Pigment Violet 19 3 Pigment Yellow155 3 Dispersing agent 0.7 0.7 0.9 0.6

TABLE 13 Example Example Example Example 13 14 15 16 Film A A A Acharacteristic evaluation Bleeding A A A A characteristic evaluation

As is apparent from Table 13, according to the two-pack light curing inkcomposition set according to the present invention, it became possibleto form a clear image having excellent film strength and additionallyexcellent curability.

While the present invention has been described in detail and withreference to specific embodiments thereof, it will be apparent to oneskilled in the art that various changes and modifications can be madetherein without departing from the spirit and scope thereof.

What is claimed is:
 1. An ink jet recording method, comprisingdischarging an ultraviolet curing ink jet ink composition on a recordingmedium, and then performing a curing reaction of the ultraviolet curingink jet ink composition by irradiation of light having a wavelength offrom 350 to 450 nm at an irradiation amount of 50 to 15,000 mJ/cm² withan ultraviolet light-emitting diode, wherein the ultraviolet curing inkjet ink composition contains 3 to 30% by weight of an urethane oligomer,50 to 95% by weight of a polymerizable compound other than the urethaneoligomer as a polymerizable monomer, and 1 to 20% by weight of aphotopolymerization initiator comprising an acylphosphineoxide; and theultraviolet curing ink jet ink composition is free from an aqueoussolvent, and wherein the polymerizable compound comprises an allylcompound and/or an N-vinyl compound, and the content of the allylcompound and/or the N-vinyl compound in the ultraviolet curing ink jetink composition is from 20 to 80% by weight.
 2. Recorded matter obtainedusing the ink jet recording method as claimed in claim
 1. 3. The ink jetrecording method as claimed in claim 1, wherein the ultraviolet curingink jet ink composition has a viscosity of 10 mPa·s or less at 25° C. 4.The ink jet recording method as claimed in claim 1, wherein thephotopolymerization initiator comprises at least one selected from thegroup consisting of bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide and2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one.5. The ink jet recording method as claimed in claim 1, wherein thepolymerizable compound comprises a multifunctional (meth)acrylate and amonofunctional or bifunctional (meth)acrylate or (meth)acrylamide. 6.The ink jet recording method as claimed in claim 1, wherein the N-vinylcompound is N-vinyl formamide.
 7. The ink jet recording method asclaimed in claim 1, wherein the photopolymerization initiator comprisesbis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide.
 8. The ink jetrecording method as claimed in claim 1, wherein the polymerizablecompound includes a polymerizable compound having PII value of 2 orless.
 9. The ink jet recording method as claimed in claim 1, wherein theurethane oligomer has a molecular weight in a range of from 500 to10,000.
 10. An ink jet recording method, comprising discharging anultraviolet curing ink jet ink composition on a recording medium, andthen performing a curing reaction of the ultraviolet curing ink jet inkcomposition by irradiation of light having a wavelength of from 350 to450 nm at an irradiation amount of 50 to 15,000 mJ/cm² with anultraviolet light-emitting diode, wherein the ultraviolet curing ink jetink composition contains at least 3 to 30% by weight of an urethaneoligomer, 50 to 95% by weight of a polymerizable compound other than theurethane oligomer as a polymerizable monomer, and 1 to 20% by weight ofa photopolymerization initiator comprising an acylphosphineoxide; andthe ultraviolet curing ink jet ink composition is free from an aqueoussolvent, and wherein the polymerizable compound comprises N-vinylformamide.
 11. Recorded matter obtained using the ink jet recordingmethod as claimed in claim
 10. 12. The ink jet recording method asclaimed in claim 10, wherein the ultraviolet curing ink jet inkcomposition has a viscosity of 10 mPa·s or less at 25° C.
 13. The inkjet recording method as claimed in claim 10, wherein thephotopolymerization initiator comprises at least one selected from thegroup consisting of bis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide and2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propionyl)-benzyl]-phenyl}-2-methyl-propan-1-one.14. The ink jet recording method as claimed in claim 10, wherein thepolymerizable compound comprises a multifunctional (meth)acrylate and amonofunctional or bifunctional (meth)acrylate or (meth)acrylamide. 15.The ink jet recording method as claimed in claim 10, wherein thephotopolymerization initiator comprisesbis(2,4,6-trimethylbenzoyl)-phenylphosphineoxide.
 16. The ink jetrecording method as claimed in claim 10, wherein the polymerizablecompound includes a polymerizable compound having PII value of 2 orless.
 17. The ink jet recording method as claimed in claim 10, whereinthe urethane oligomer has a molecular weight in a range of from 500 to10,000.